Method for transmitting an uplink signal, method for receiving an uplink signal, user equipment, and base station

ABSTRACT

The invention relates to a method comprising classifying user equipment (UE) cells, to which carrier aggregation is applied, into a plurality of time advance groups. Uplink-time synchronization is managed using the time synchronization of a primary cell (Pcell) in the time synchronization group to which the primary cell belongs. For other time synchronization groups, the uplink time synchronization is managed using the time synchronization of a secondary cell (SCell) that is particularly set in the relevant time synchronization group. Thus, the plurality of time synchronizations can be effectively managed for the UE and a base station (BS).

CROSS REFERENCE TO RELATED APPLICATIONS

The present application is a continuation of U.S. patent applicationSer. No. 14/749,053, filed on Jun. 24, 2015 (now U.S. Pat. No.9,596,701), which is a continuation of U.S. patent application Ser. No.14/008,014, filed on Sep. 27, 2013 (now U.S. Pat. No. 9,118,452), theentire disclosure of each of which is hereby incorporated by referencefor all purposes as if fully set forth herein. U.S. patent applicationSer. No. 14/008,014 is a U.S. National Stage Entry of PCT InternationalApplication No. PCT/KR2012/002202, filed on Mar. 27, 2012, and claimsthe benefit of U.S. Provisional Application No. 61/468,565, filed onMar. 28, 2011.

TECHNICAL FIELD

The present invention relates to a wireless communication system, andmore particularly, to a method and apparatus for transmitting andreceiving uplink and downlink signals more effectively under a carrieraggregation of a plurality of cells.

BACKGROUND ART

A general wireless communication system performs data transmission andreception through one downlink (DL) band and one uplink (UL) bandcorresponding to the downlink (in case of a frequency division duplex(FDD) mode), or divides a predetermined radio frame into uplink timeunit(s) and downlink time unit(s) in a time domain and performs datatransmission and reception through the uplink and downlink time units(in case of a time division duplex (TDD) mode). A base station (BS) anda user equipment (UE) transmit and receive data and/or controlinformation scheduled in a predetermined time unit, for example, asubframe unit. The data are transmitted and received through a dataregion configured for uplink and downlink subframes, and the controlinformation is transmitted and received through a control regionconfigured for the uplink and downlink subframes. To this end, variousphysical channels carrying radio signals are configured in the uplinkand downlink subframes.

Meanwhile, in the recent wireless communication system, the carrieraggregation (or bandwidth aggregation) technology, which uses greateruplink and downlink bandwidths by aggregating a plurality of uplink anddownlink frequency blocks, has been discussed to use a wider frequencyband.

FIG. 1 is a diagram illustrating an example of communication performedunder a multi-carrier status.

A multicarrier system or carrier aggregation system refers to a systemthat together aggregates a plurality of carriers having a bandwidthsmaller than that of a target band to support a broadband. The carrieraggregation technology is different from the orthogonal frequencydivision multiplexing (OFDM) technology in that downlink or uplinkcommunication is performed using a plurality of carrier frequencies. Inthe OFDM technology, downlink or uplink communication is performed bycarrying a basic frequency band, which is divided into a plurality ofsubcarriers, in one carrier frequency. When a plurality of carriershaving a bandwidth smaller than that of a target band are aggregated,for backward compatibility with the system according to the related art,a bandwidth of aggregated bands may be limited to a bandwidth used inthe system of the related art. For example, the LTE system according tothe related art supports bandwidths of 1.4, 3, 5, 10, 15 and 20 MHz, andthe LTE-A system evolved from the LTE system may support a bandwidthgreater than 20 MHz by using the bandwidths only supported by the LTEsystem. Alternatively, the LTE-A system may support carrier aggregationby defining a new bandwidth regardless of the bandwidth used in thesystem according to the related art. Multicarrier refers to aterminology that may be used together with carrier aggregation andbandwidth aggregation. Also, carrier aggregation refers to bothcontiguous carrier aggregation and non-contiguous carrier aggregation.For reference, if one component carrier (CC) is only used forcommunication in a TDD mode, or if one UL CC and one DL CC are only usedfor communication in a FDD mode, this communication corresponds to thatperformed under a single carrier situation (non-CA).

DISCLOSURE Technical Problem

Under a multicarrier aggregation status where a plurality of carriersare aggregated and used for communication between a base station BS anda user equipment UE, a communication method based on a single carriercannot be applied to communication based on multiple carriers. A newcommunication method, which is suitable for communication based on aplurality of carriers while minimizing an influence on the existingsystem, should be defined.

It will be appreciated by persons skilled in the art that the objectsthat could be achieved with the present invention are not limited towhat has been particularly described hereinabove and the above and otherobjects that the present invention could achieve will be more clearlyunderstood from the following detailed description.

Technical Solution

In one aspect of the present invention, a method for transmitting, by ause equipment configured with a plurality of cells, an uplink signal toa base station, comprises: receiving information indicating a specialsecondary cell (SCell) for a random access procedure, among one or moreSCells within an SCell group comprised of the one or more SCells, fromthe base station; performing the random access procedure on the specialSCell; and transmitting an uplink signal for the one or more SCellswithin the SCell group to the base station on the special SCell througha PUCCH, wherein the SCell group is different from a PCell group whichincludes at least a primary cell (PCell) of the plurality of cells.

In another aspect of the present invention, a method for receiving, by abase station, an uplink signal from a user equipment configured with aplurality of cells, comprises: transmitting information indicating aspecial secondary cell (SCell) for a random access procedure, among oneor more SCells within an SCell group comprised of the one or moreSCells, to the user equipment; performing the random access procedurewith the user equipment on the special SCell; and receiving an uplinksignal for the one or more SCells within the SCell group from the userequipment on the special SCell through a PUCCH, wherein the SCell groupis different from a PCell group, which includes at least a primary cell(PCell) of the plurality of cells.

In still another aspect of the present invention, a user equipment,which is configured with a plurality of cells, for transmitting anuplink signal to a base station, comprises: a radio frequency (RF) unitconfigured to transmit or receive a radio signal; and a processorconfigured to control the RF unit, wherein the processor controls the RFunit to receive information indicating a special secondary cell (SCell)for a random access procedure, among one or more SCells within an SCellgroup comprised of the one or more SCells, from the base station,controls the RF unit to perform the random access procedure on thespecial SCell, and controls the RF unit to transmit an uplink signal forthe one or more SCells within the SCell group to the base station on thespecial SCell through a PUCCH, wherein the SCell group is different froma PCell group which includes at least a primary cell (PCell) of theplurality of cells.

In further still another aspect of the present invention, a base stationfor receiving an uplink signal from a user equipment configured with aplurality of cells, comprises: a radio frequency (RF) unit configured totransmit or receive a radio signal; and a processor configured tocontrol the RF unit, wherein the processor controls the RF unit totransmit information indicating a special secondary cell (SCell) for arandom access procedure, among one or more SCells within an SCell groupcomprised of the one or more SCells, to the user equipment, and controlsthe RF unit to perform the random access procedure with the userequipment on the special SCell, and controls the RF unit to receive anuplink signal for the one or more SCells within the SCell group from theuser equipment on the special SCell through a PUCCH, wherein the SCellgroup is different from a PCell group which includes at least a primarycell (PCell) of the plurality of cells.

In each aspect of the present invention, a timing advance command (TAC)for the special SCell from the base station may be transmitted from thebase station to the user equipment in response to the random accessprocedure performed on the special S cell, and the base station and theuser equipment may apply the TAC to every cell within the SCell group.

In each aspect of the present invention, information indicating releaseof the special SCell may be transmitted from the base station to theuser equipment, and the base station and the user equipment may releaseevery cell within the SCell group in accordance with the informationindicating release of the special SCell.

In each aspect of the present invention, information indicatingdeactivation of the special SCell may be transmitted from the basestation to the user equipment, and the base station and the userequipment may deactivate every cell within the SCell group in accordancewith the information indicating deactivation of the special SCell.

In each aspect of the present invention, a deactivation timer for thespecial SCell may be transmitted from the base station to the userequipment, and the base station and the user equipment may apply thedeactivation timer to every cell within the SCell group.

In each aspect of the present invention, the base station and the userequipment may release or deactivate every cell within the SCell group incase of radio link failure for the special SCell.

The aspects of the present invention are only a part of the preferredembodiments of the present invention, and various embodiments based ontechnical features of the present invention may be devised andunderstood by the person with ordinary skill in the art based on thedetailed description of the present invention.

Advantageous Effects

According to the present invention, uplink carriers where the userequipment UE and the base station BS are operated on differentfrequencies and/or uplink carriers where the user equipment UE and thebase station BS are operated on frequencies, which use antennas ofdifferent locations, may be aggregated.

Also, according to the present invention, a plurality of time advancesmay be managed efficiently for one user equipment UE.

Also, according to the present invention, different time advances may beapplied to uplink CCs having different frequency features.

It will be appreciated by persons skilled in the art that that theeffects that could be achieved with the present invention are notlimited to what has been particularly described hereinabove and otheradvantages of the present invention will be more clearly understood fromthe following detailed description.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are included to provide a furtherunderstanding of the invention and are incorporated in and constitute apart of this application, illustrate embodiment(s) of the invention andtogether with the description serve to explain the principle of theinvention. In the drawings:

FIG. 1 is a diagram illustrating an example of communication performedunder a multi-carrier status;

FIG. 2 is a diagram illustrating a structure of a wireless communicationsystem;

FIG. 3 and FIG. 4 are diagrams respectively illustrating a control planeand a user plane of a radio protocol;

FIG. 5 is a diagram illustrating a structure of a downlink L2 (secondlayer) in carrier aggregation;

FIG. 6 is a diagram illustrating a structure of an uplink L2 (secondlayer) in carrier aggregation;

FIG. 7 is a diagram illustrating an operation of a user equipment UE,which is associated with radio link failure;

FIG. 8 and FIG. 9 are diagrams illustrating an operation of a userequipment UE in an RRC connection reestablishment procedure;

FIG. 10 is a diagram illustrating an operation procedure of a userequipment UE and a base station BS in a contention based random accessprocedure;

FIG. 11 is a diagram illustrating an operation procedure of a userequipment UE and a base station BS in a non-contention based randomaccess procedure;

FIG. 12 is a diagram illustrating an example of a PHR MAC controlelement (CE) format transmitted from a user equipment UE, which includescarrier aggregation, to a base station BS;

FIG. 13 is a diagram illustrating a random access procedure according tothe embodiments of the present invention; and

FIG. 14 is a block diagram illustrating a transmission apparatus 10 anda reception apparatus 20, which perform the present invention.

FIG. 15 is a radio link monitoring procedure according to theembodiments of the claimed invention.

BEST MODE FOR CARRYING OUT THE INVENTION

The following embodiments are achieved by combination of structuralelements and features of the present invention in a predetermined type.Each of the structural elements or features should be consideredselectively unless specified separately. Each of the structural elementsor features may be carried out without being combined with otherstructural elements or features. Also, some structural elements and/orfeatures may be combined with one another to constitute the embodimentsof the present invention. The order of operations described in theembodiments of the present invention may be changed. Some structuralelements or features of one embodiment may be included in anotherembodiment, or may be replaced with corresponding structural elements orfeatures of another embodiment.

In this specification, the embodiments of the present invention havebeen described based on the data transmission and reception between abase station BS and a user equipment UE. In this case, the base stationBS means a terminal node of a network, which performs directcommunication with the user equipment UE. A specific operation which hasbeen described as being performed by the base station may be performedby an upper node of the base station BS as the case may be. In otherwords, it will be apparent that various operations performed forcommunication with the user equipment UE in the network which includes aplurality of network nodes along with the base station may be performedby the base station BS or network nodes other than the base station BS.The base station BS may be replaced with terms such as a fixed station,Node B, eNode B (eNB), and an access point (AP). A relay node may bereplaced with terms such as a relay node (RN) and a relay station (RS).Also, the user equipment UE may be replaced with terms such as aterminal, a mobile station (MS), a mobile subscriber station (MSS), anda subscriber station (SS).

In the present invention, a Physical Downlink Control Channel (PDCCH)and a Physical Downlink Shared Channel (PDSCH) are sets oftime-frequency resources or resource element (REs), which carry DownlinkControl Information (DCI) and downlink data, respectively. Also, aPhysical Uplink Control Channel (PUCCH), a Physical Uplink SharedChannel (PUSCH), and a Physical Random Access Channel (PRACH) are setsof time-frequency resources or resource elements, which carry UplinkControl Information (UCI), uplink data, and a random access signal,respectively. In the present invention, if it is said that a userequipment UE transmits a PUCCH, a PUSCH and a PRACH, this may mean thatthe UE transmits UCI, uplink data and a random access signal on thePUCCH, the PUSCH and the PRACH, respectively. In addition, if it is saidthat a base station BS transmits a PDCCH and a PDSCH, this may mean thatthe base station BS transmits downlink data and control information onthe PDCCH and the PDSCH, respectively.

Specific terminologies hereinafter used in the embodiments of thepresent invention are provided to assist understanding of the presentinvention, and various modifications may be made in the specificterminologies within the range that they do not depart from technicalspirits of the present invention.

In some cases, to prevent the concept of the present invention frombeing ambiguous, structures and apparatuses of the known art will beomitted, or will be shown in the form of a block diagram based on mainfunctions of each structure and apparatus. Also, wherever possible, thesame reference numbers will be used throughout the drawings and thespecification to refer to the same or like parts.

The embodiments of the present invention may be supported by standarddocuments disclosed in at least one of wireless access systems, i.e.,IEEE 802 system, 3GPP system, 3GPP LTE system, 3GPP LTE, 3GPP LTE-A(LTE-Advanced) system, and 3GPP2 system. Namely, among the embodimentsof the present invention, apparent steps or parts, which are notdescribed to clarify technical spirits of the present invention, may besupported by the above documents. Also, all terminologies disclosedherein may be described by the above standard documents.

The following technology may be used for various wireless access systemssuch as CDMA (code division multiple access), FDMA (frequency divisionmultiple access), TDMA (time division multiple access), OFDMA(orthogonal frequency division multiple access), and SC-FDMA (singlecarrier frequency division multiple access). The CDMA may be implementedby the radio technology such as universal terrestrial radio access(UTRA) or CDMA2000. The TDMA may be implemented by the radio technologysuch as global system for mobile communications (GSM)/general packetradio service (GPRS)/enhanced data rates for GSM evolution (EDGE). TheOFDMA may be implemented by the radio technology such as IEEE 802.11(Wi-Fi), IEEE 802.16 (WiMAX), IEEE 802.20, and evolved UTRA (E-UTRA).The UTRA is a part of a universal mobile telecommunications system(UMTS). A 3^(rd) generation partnership project long term evolution(3GPP LTE) communication system is a part of an evolved UMTS (E-UMTS)that uses E-UTRA, and uses OFDMA in a downlink while uses SC-FDMA in anuplink. LTE-advanced (LTE-A) is an evolved version of the 3GPP LTEsystem. WiMAX may be described by the IEEE 802.16e standard(WirelessMAN-OFDMA Reference System) and the advanced IEEE 802.16mstandard (WirelessMAN-OFDMA Advanced system). Although the followingdescription will be based on the 3GPP LTE system and the 3GPP LTE-Asystem to clarify description, it is to be understood that technicalspirits of the present invention are not limited to the 3GPP LTE and the3GPP LTE-A system.

Structure of LTE System

FIG. 2 is a diagram illustrating a structure of a wireless communicationsystem.

A system structure of the LTE system, which is an example of thewireless communication system to which the present invention may beapplied, will be described with reference to FIG. 2. The LTE system is amobile communication system evolved from the UMTS. As shown in FIG. 2,the LTE system may be divided into E-UTRAN (Evolved UMTS TerrestrialRadio Access Network) and EPC (Evolved Packet Core). The E-UTRANincludes a user equipment UE and eNB (Evolved NodeB, base station). Aninterface between the UE and the eNB may be referred to as Uu interface,and an interface between eNBs may be referred to as X2 interface. TheEPC includes a mobility management entity (MME) and a serving-gateway(S-GW), wherein the MME serves as a control plane and the servinggateway serves as a user plane. An interface between the eNB and the MMEmay be referred to as S1-MME interface, and an interface between the eNBand the S-SG may be referred to as S1-U interface. The S1-MME interfaceand the S1-U interface may be referred to as S1 interface.

A radio interface protocol is defined in the Uu interface which is aradio interval, and horizontally includes a physical layer, a data linklayer, and a network layer, and vertically includes a user plane fordata information transfer and a control plane for signaling transfer(control signal transfer). As shown in FIG. 2 and FIG. 3, the radiointerface protocol may be classified into L1 (first layer) including aphysical (PHY) layer, L2 (second layer) including MAC/RLC/PDCP (mediumaccess control/radio link control/protocol data convergence protocol)layers, and L3 (third layer) including RRC layer, based on three lowerlayers of the open system interconnection (OSI) standard model widelyknown in the communications systems. These radio protocol layers existin the user equipment UE and the E-UTRAN in pairs, and play a role indata transfer of the Uu interface.

FIG. 3 and FIG. 4 are diagrams respectively illustrating a control planeand a user plane of a radio protocol.

Referring to FIG. 3 and FIG. 4, the physical (PHY) layer belonging tothe first layer L1 provides an information transfer service using aphysical channel. The PHY layer is connected to a medium access control(MAC) layer above the physical layer via a transport channel. Data aretransferred between the medium access control layer and the physicallayer via the transport channel. At this time, the transport channel isdivided into a dedicated transport channel and a common transportchannel depending channel sharing. Data are transferred between onephysical layer of a transmitting side and the other physical layer of areceiving side through the physical channel.

Several layers exist in the second layer. First of all, the MAC layerserves to map various logical channels into various transport channels,and also serves as logical channel multiplexing for mapping severallogical channels into one transport channel. The MAC layer is connectedwith a radio link control (RLC) layer through a logical channel, whereinthe RLC layer is located above the MAC layer. The logical channel isdivided into a control channel transmitting information of the controlplane and a traffic channel transmitting information of the user planedepending on types of transmitted information.

The RLC layer of the second layer serves to perform segmentation andconcatenation of data received from its upper layer to control a size ofthe data so that the lower layer transmits the data to a radio interval.Also, the RLC layer of the second layer provides three action modes,i.e., a transparent mode (TM), an un-acknowledged mode (UM), and anacknowledged mode (AM) to ensure various quality of services (QoS)required by each radio bearer (RB). In particular, the AM RLC layerperforms a retransmission function through automatic repeat and request(ARQ) function for reliable data transmission.

In order to effectively transmit data using IP packets such as IPv4 orIPv6 within a radio-communication interval having a narrow bandwidth, aPDCP (packet data convergence protocol) layer of the second layerperforms header compression to reduce the size of IP packet headerhaving relatively great size and unnecessary control information. Theheader compression is to increase transmission efficiency of theradio-communication interval by allowing a packet header of data totransmit necessary information only. Also, in the LTE system, the PDCPlayer performs a security function. The security function includes aciphering function preventing the third party from performing datamonitoring and an integrity protection function preventing the thirdparty from performing data manipulation.

A radio resource control (RRC) layer located on the highest part of thethird layer is defined in the control plane only and is associated withconfiguration, reconfiguration and release of radio bearers (RBs) to bein charge of controlling the logical, transport and physical channels.In this case, the RB means a service or logical path provided by thefirst and second layers of the radio protocol for the data transferbetween the user equipment and the UTRAN. Generally, establishing RBmeans that features of a radio protocol layer and channel required for aspecific service are defined and their detailed parameters and actionmethods will be established. The RB is divided into a signaling RB (SRB)and a data RB (DRB). The SRB is used as a passageway for transmittingRRC message in the control plane, and the DRB is used as a passagewayfor transmitting user data in the user plane.

Carrier Aggregation Technology

Meanwhile, as described with reference to FIG. 1, the carrieraggregation or bandwidth aggregation technology has been recentlydiscussed. For example, referring to FIG. 1, the carrier aggregationtechnology may support a system bandwidth of maximum 100 MHz by usingfive component carriers (CCs) of 20 MHz grouped on each of the uplinkand the downlink. The respective CCs may adjoin each other or not in thefrequency domain. Although FIG. 1 illustrates that a bandwidth of UL CCis the same as that of DL CC, bandwidths of the respective CCs may bedefined independently. Also, asymmetric carrier aggregation where thenumber of UL CCs is different from the number of DL CCs may beperformed. The UL CC and the DL CC may be referred to as UL resourcesand DL resources, respectively. Even though the base station BS controlsX number of DL CCs, a frequency band that may be received by a specificuser equipment may be limited to Y(≦X) number of DL CCs. In this case,the user equipment UE monitors DL signal and data transmitted throughthe Y number of CCs. Also, even though the base station BS controls Lnumber UL CCs, a frequency band that may be transmitted from a specificuser equipment UE may be limited to M(≦L) number of UL CCs. In this way,the DL/UL CC limited to the specific user equipment UE may be referredto as serving UL/DL CC configured by the specific UE.

CCs used for carrier aggregation may be classified into a primarycomponent carrier (PCC) and secondary component carriers (SCC). Theprimary component carrier means a carrier used to exchange traffic andcontrol signaling between the base station and the user equipment.Control signaling may include addition of component carriers,configuration for the primary component carrier, uplink (UL) grant, anddownlink (DL) assignment. Although a plurality of component carriers(CCs) are used by the base station, the user equipment connected to thebase station may be configured to have only one primary componentcarrier. If the user equipment is operated in a single carrier mode, theprimary component carrier is used. According to single carriercommunication, one PCC is used for communication between the userequipment UE and the base station BS, whereas SCC is not used forcommunication. Accordingly, all requirements required for exchange ofdata and control signaling between the base station and the userequipment should be fulfilled so that the primary component carrier maybe used independently.

In the mean time, the secondary component carrier means an additionalcomponent carrier that may be configured after RRC connection isestablished between the user equipment UE and the base station BS. TheSCC may form a set of serving CCs for the UE together with the PCCaccording to capability of the UE. The SCC may be activated ordeactivated depending on data requirements transmitted and received. TheSCC may be configured to be used only by a specific command and rulereceived from the base station. Also, the SCC may be configured to beused together with the PCC to support additional bandwidth. Controlinformation such as uplink grant or downlink assignment may be receivedfrom the base station to the user equipment through a PDCCH or PDSCH ofthe activated SCC, and uplink control information such as channel stateinformation (for example, a channel quality indicator (CQI), a precodingmatrix index (PMI), and a rank indicator (RI)) be transmitted from theuser equipment to the base station through a PUCCH.

In the meantime, the 3GPP LTE(-A) system uses a concept of cell tomanage radio resources. In view of the radio resources, the cell isdefined by combination of downlink resources and uplink resources, thatis, combination of DL CC and UL CC. The cell may be configured bydownlink (DL) resources only, or may be configured by combination ofdownlink resources and uplink resources. If carrier aggregation issupported, linkage between carrier frequency of the downlink resources(or DL CC) and carrier frequency of the uplink resources (or UL CC) maybe indicated by system information. For example, combination of DLresources and UL resources may be indicated by system information blocktype2 (SIB2) linkage. In case of the FDD, since UL operating band isdifferent from UL operating band, different carrier frequencies arelinked to constitute one cell, and the SIB2 linkage indicates afrequency different from that of DL CC accessed by the UE as thefrequency of the UL CC. In other words, in case of the FDD, the DL CCand the UL CC linked with the DL CC to constitute one cell are operatedat their respective frequencies different from each other. In case ofthe TDD, since the UL operating band is the same as the DL operatingband, one carrier frequency constitutes one cell, and the SIB2 linkageindicates the same frequency as that of the DL CC accessed by the UE asthe frequency of the corresponding UL CC. In other words, in case of theTDD, the DL CC and the UL CC linked with the DL CC to constitute onecell are operated at the same frequency. In this case, the carrierfrequency means a center frequency of each cell or CC. Hereinafter, thecell operated on the primary frequency will be referred to as a primarycell (PCell) or PCC, and the cell operated on the secondary frequency(or SCC) will be referred to as a secondary cell (SCell) or SCC.

For reference, the terminology ‘cell’ used in carrier aggregation isdifferent from the terminology ‘cell’ indicating a certain geographicalarea where a communication service is provided by one antenna group. Inorder to identify the cell indicating a certain geographical area fromthe cell of carrier aggregation, the cell of carrier aggregation will bereferred to as CC and the cell of the geographical area will be referredto as a cell in the following embodiments of the present invention.

Resource allocation to the user equipment may be performed in the rangeof a primary component carrier or one or more PCCs. If carrieraggregation is configured, the system may allocate the SCC to the userequipment asymmetrically to the downlink and/or the uplink, on the basisof system load (that is, static/dynamic load balancing), peak data rate,or service quality request. In use of the carrier aggregationtechnology, configuration for the component carriers is provided fromthe base station to the user equipment after RRC connection procedure.RRC connection means that the user equipment is allocated with a radioresource on the basis of RRC signaling exchanged between the RRC layerof the user equipment and a network through SRB. After RRC connectionprocedure of the user equipment and the base station is performed, theuser equipment may receive configuration information on the primarycomponent carrier and/or the secondary component carrier(s) from thebase station. The configuration information on the secondary componentcarriers may include addition/release (or activation/deactivation) ofthe secondary component carriers. Accordingly, in order to activate thesecondary component carriers between the base station and the userequipment or deactivate the existing secondary component carriers,exchange of RRC signaling and MAC control elements is required.Activation or deactivation of the secondary component carriers may bedetermined by the base station on the basis of quality of service (QoS),load condition of carriers, and the other factors. The base station maycommand the user equipment to configure the secondary component carriersby using a control message that includes information such as commandtype (activation/deactivation) on the downlink/uplink and a list ofsecondary component carriers. However, once the primary componentcarrier is allocated to the user equipment UE, it is not deactivated ifCC allocation for the user equipment UE is reconfigured or unless theuser equipment UE performs handover.

Uplink/Downlink L2 Structure Considering Carrier Aggregation

FIG. 5 is a diagram illustrating a structure of a downlink L2 (secondlayer) in carrier aggregation, and FIG. 6 is a diagram illustrating astructure of an uplink L2 (second layer) in carrier aggregation. Astructure of L2 (second layer) considering carrier aggregationtechnology will be described with reference to FIG. 5 and FIG. 6.

In a downlink L2 structure 500 of FIG. 5, a PDCP layer 510, an RLC layer520 and a MAC layer 530 are shown. In FIG. 5, elements 505, 515, 525 and535 marked with circles in an interface between the respective layersrepresent service access points (SAP) for peer-to-peer communication.The SAP between a PHY channel (not shown) and the MAC layer provides atransport channel (535), and the SAP between the MAC layer and the RLClayer provides a logical channel (525). A general operation of eachlayer has been described above.

The MAC layer multiplexes a plurality of logical channels (that is,radio bearers) from the RLC layer. In the downlink L2 structure, aplurality of multiplexing entities 531 of the MAC layer are related toapplication of the multiple input multiple output (MIMO) technology. Ina system that does not consider the carrier aggregation technology,since one transport channel is generated by multiplexing a plurality oflogical channels in case of non-MIMO, one hybrid automatic repeat andrequest (HARQ) entity is provided to one multiplexing entity (notshown).

In the meantime, in a system that considers the carrier aggregationtechnology, a plurality of transport channels corresponding to aplurality of CCs are generated from one multiplexing entity 531. In thisregard, in the carrier aggregation technology, one HARQ entity 532manages one CC. Accordingly, the MAC layer 530 of the system thatsupports the carrier aggregation technology provides a plurality of HARQentities 532 to one multiplexing entity 531. Also, since the respectiveHARQ entities 532 process a transport block independently, they maytransmit and receive a plurality transport blocks through a plurality ofCCs at the same time.

In an uplink structure 600 of FIG. 6, the same operation as that of thedownlink L2 structure 500 of FIG. 5 is performed except that onemultiplexing entity 630 is included in one MAC layer 630. In otherwords, a plurality of HARQ entities 632 are provided for a plurality ofCCs, the operations related to the plurality of HARQ entities 632 areperformed by the MAC layer 630, and the plurality of transport blocksare transmitted and received through the plurality of CCs at the sametime.

Uplink Time Advance Maintenance

In the 3GPP LTE(-A) system based on the orthogonal frequency divisionmultiplex (OFDM) technology, the time required for a signal transmittedfrom the user equipment UE to reach the base station BS may be varieddepending on a radius of the cell, a location of the user equipment UEwithin the cell, and a moving speed of the user equipment UE. In otherwords, if the base station BS does not manage transmission timing peruser equipment UE, a transport signal of a specific user equipment UEmay interfere with a transport signal transmitted from another userequipment UE, whereby an error rate of a received signal is increased atthe base station BS. In more detail, in case of the user equipment UEthat tries to transmit a signal at the cell edge, the time required forthe transmitted signal to reach the base station BS is longer than thetime required for the transport signal of the user equipment UE locatedat the center of the cell to reach the base station BS. On other hand,the time required for the transport signal of the user equipment UElocated at the center of the cell to reach the base station BS willrelatively be shorter than the time required for the transport signal ofthe user equipment UE located at the cell edge to reach the base stationBS. In view of the base station BS, in order to avoid interference,since data or signals transmitted from all the UEs within the cellshould be received within every effective time boundary, the basestation BS should appropriately control transmission timing of the userequipment UE in accordance with the status of the user equipment UE.This control will be referred to as time advance maintenance or timealignment maintenance.

As one method for manage uplink time alignment, a random accessprocedure may be provided. In other words, the base station BS receivesa random access preamble from the user equipment UE through the randomaccess procedure, and calculates a time advance value for makingtransmission timing of the user equipment UE fast or slow, by usingreceived information of the random access preamble. And, the basestation BS notifies the user equipment UE of the calculated time advancevalue through a random access response, and the user equipment UEupdates transmission timing by using the value. As another method formanage uplink time alignment, a method based on a sounding referencesignal (SRS) may be provided. The base station BS receives the SRS fromthe user equipment UE periodically or randomly, calculates a timeadvance value of the user equipment UE through the received signal, andnotifies the user equipment UE of the calculated time advance valuethrough the received signal. As a result, the user equipment UE updatesits transmission timing.

As described above, the base station BS measures the transmission timingof the user equipment UE by using the random access preamble or the SRS,calculates a timing value for correction, and notifies the userequipment UE of the calculated timing value. The time advance value(that is, timing value for correction) transmitted from the base stationBS to the user equipment UE will be referred to as a timing advancecommand. The timing advance command is processed by the MAC layer. Sincethe user equipment UE does not always exist at a fixed location, thetransmission timing of the user equipment UE is varied every timedepending on the moving speed of the user equipment UE, the location ofthe user equipment UE, etc. Considering this, it is assumed that thetiming advance command is valid for a specific time period not aninfinite time if the user equipment UE receives the timing advancecommand from the base station BS. In order to count the specific timeassuming that the timing advance command is valid, the user equipment UEuses a time alignment timer. If the user equipment UE receives thetiming advance command from the base station BS, the user equipment UEinitiates the time alignment timer. It is assumed that the uplink timeadvance of the user equipment UE is synchronized with the uplink timeadvance of the base station BS, i.e., the uplink time is aligned onlywhen the time alignment timer is operating. A value of the timealignment timer may be transferred from the base station BS to the userequipment UE through RRC signal such as system information or radiobearer reconfiguration. Also, if the user equipment UE receives a newtiming advance command from the base station BS while the time alignmenttimer is operating, the user equipment UE resets the time alignmenttimer. If the time alignment timer expires, or if the time alignmenttimer is not operating, the user equipment UE assumes that its timeadvance is not synchronized with the time advance of the base stationBS, and does not transmit any uplink signal, for example, a physicaluplink shared channel (PUSCH) and a physical uplink control channel(PUCCH), except for the random access preamble.

Radio Link Monitoring

In the present invention, communication of the user equipment UE with aspecific cell means that the user equipment UE performs communicationwith the base station BS, antenna or antenna group, which provides acommunication service to the specific cell. Also, a downlink or uplinksignal of the specific cell means a downlink or uplink signal receivedby or transmitted from the user equipment UE from or to the base stationBS, antenna or antenna group, which provides a communication service tothe specific cell. Channel status/quality of the specific cell meanschannel status/quality of a channel or communication link formed betweenthe base station BS, antenna or antenna group and a predetermined UE.

The user equipment UE continues to perform measurement to maintaincommunication link quality with the cell that provides a service to theuser equipment UE. In particular, the user equipment UE determineswhether the communication link quality with the cell that provides aservice thereto is in available communication status or not. If the userequipment UE determines that quality of the cell is not good to performcommunication, the user equipment UE declares radio link failure (RLF).If the user equipment UE declares radio link failure, the user equipmentUE does not maintain communication with the corresponding cell, selectsa cell through a cell selection procedure, and then tries RRC connectionre-establishment.

FIG. 7 is a diagram illustrating an operation of a UE, which isassociated with radio link failure. Referring to FIG. 7, the operationof the user equipment UE, which is related to radio link failure, may bedescribed as two phases as follows.

At the first phase, the user equipment UE tests whether there is anyproblem in a current radio communication link. If there is a problem inthe radio link, the user equipment UE declares radio link failure andwaits for a certain time period T1 whether the communication link isrecovered. If the corresponding link is recovered for the time periodT1, the user equipment UE continues to perform normal operation. If theradio link problem detected at the first phase is not solved for thetime period T1, the user equipment UE declares radio link failure andenters the second phase. At the second phase, for recovery from theradio link failure, the user equipment UE performs RRC connectionre-establishment procedure. The RRC connection re-establishmentprocedure is that RRC connection is re-established in the RRC connectionstate (RRC_CONNECTED). Since the user equipment UE stays in the RRCconnection state (RRC_CONNECTED), that is, the user equipment UE doesnot enter the RRC idle state (RRC_IDLE), the user equipment UE does notreset all of its radio configurations (for example, radio bearerconfigurations). Instead, the user equipment UE temporarily suspends useof all the radio bearers except for SRB0 when starting the RRCconnection re-establishment procedure. If the RRC connectionre-establishment is performed successfully, the user equipment UEresumes use of the radio bearers of which use is temporarily suspended.However, if the user equipment UE does not complete RRC connectionre-establishment for a certain time period T2, the user equipment UEenters the RRC idle state.

FIG. 8 and FIG. 9 are diagrams illustrating an operation of UE in an RRCconnection re-establishment procedure. The RRC connectionre-establishment procedure is performed to re-establish RRC connectioninvolved in resume of SRB2 operation, re-activation of security, andconfiguration of PCC only. The user equipment UE of which security isactivated and which is in RRC connection state may initiate the RRCconnection re-establishment procedure to continue to perform RRCconnection.

The operation of the user equipment UE in the RRC connectionre-establishment procedure will be described in more detail withreference to FIG. 8 and FIG. 9. First of all, the user equipment UEselects one cell by performing cell selection. The user equipment UEreceives system information from the selected cell to receive basicparameters for access to the cell. Subsequently, the user equipment UEtries RRC connection re-establishment through the random accessprocedure. The user equipment UE, which has received random accessresponse, transmits an RRC connection re-establishment request messageRRCConnectionReestablishmentRequest to the base station BS tore-establish RRC connection (S801). If the base station BS of the cellselected by the user equipment UE through RRC cell selection has acontext of the user equipment UE, that is, if the selected cell is aprepared cell, the base station BS of the corresponding cell may acceptRRC connection re-establishment request by transmitting an RRCconnection re-establishment message RRCConnectionReestablishment to theuser equipment UE (S802). If the base station BS acceptsre-establishment, the operation of the other radio bearers is maintainedin a stopped state, but SRB1 operation is resumed. The user equipmentUE, which has received the RRC connection re-establishment message, mayre-establish RRC connection and transmit an RRC connectionre-establishment complete message RRCConnectionReestablishmentCompleteto the base station BS. As a result, RRC connection re-establishment maybe performed successfully. However, if the cell selected by the userequipment UE is not a prepared cell, since the base station BS of thecorresponding cell does not have a context of the user equipment UE,even though the base station BS receives the RRC connectionre-establishment request message from the user equipment UE (S901), itcannot accept the RRC connection re-establishment request of the userequipment UE. Accordingly, the base station BS transmits an RRCconnection re-establishment reject messageRRCConnectionReestablishmentReject to the user equipment UE (S902). As aresult, the RRC connection re-establishment procedure is failed.

Random Access Procedure

Hereinafter, a random access procedure performed by the 3GPP LTE systemwill be described in more detail.

In the 3GPP LTE system, the user equipment UE may perform the randomaccess procedure in case of the following cases.

-   -   Case where the user equipment UE performs initial access due to        no RRC connection with the base station BS.    -   Case where the user equipment UE initially accesses a target        cell during a handover procedure.    -   Case where the random access procedure is requested by a command        of the base station BS.    -   Case where uplink data occur in a state that uplink time advance        is not synchronized or a designated radio resource is not        allocated.    -   Case where a recovery procedure is performed during radio link        failure or handover failure.

A random access preamble is used for the random access procedure. Therandom access procedures are classified into a contention based randomaccess procedure and a non-contention based random access procedure inaccordance with a procedure of selecting a random access preamble. Inthe contention based random access procedure, the user equipment UErandomly selects one of a set of random access preambles and uses theselected one. In the non-contention based random access procedure, aspecific UE uses a random access preamble allocated thereto from thebase station BS. The contention based random access procedure isdifferent from the non-contention based random access procedure inoccurrence of contention. The non-contention based random accessprocedure may be used only in case of request based on the handoverprocedure or the command of the base station BS.

FIG. 10 is a diagram illustrating an operation procedure of UE and BS ina contention based random access procedure.

1. Random Access Preamble

In case of contention based random access, the user equipment UE mayrandomly select one random access preamble from a set of random accesspreambles indicated through system information or handover command, andmay select a physical random access channel (PRACH), through which therandom access preamble may be transmitted and transmit the selected one(S1001).

2. Random Access Response

After transmitting the random access preamble, the user equipment UEtries to receive its random access response within a random accessreceiving window indicated by the base station BS through the systeminformation or handover command (S1002). In more detail, the randomaccess response information may be transmitted in the form of MAC PDU(packet data unit). The MAC PDU may be transferred through a physicaldownlink shared channel (PDSCH). Also, in order to appropriately receivethe information through the PDSCH, the user equipment UE may monitor aphysical downlink control channel (PDCCH). The PDCCH may includeinformation of the user equipment UE, which should receive the PDSCH,frequency and time information of a radio resource of the PDSCH, and atransmission format of the PDSCH. Once the user equipment UE receivesthe PDCCH successfully, it may appropriately receive the random accessresponse transmitted to the PDSCH in accordance with the information ofthe PDCCH. The random access response may include a random accesspreamble identifier (ID) (RAPID), uplink (UL) grant indicating uplinkradio resources, a temporary cell radio network temporary identifier(C-RNTI) (hereinafter, referred to as temporary cell identifier) and atime advance correction value (for example, timing advance command(TAC)). Since random access responses for one or more user equipmentsUEs may be included in one random access response timing, the randomaccess preamble identifier is required for random access response toindicate a user equipment UE for which the UL grant, the temporary cellidentifier and the TAC are effective. The user equipment UE may receivethe UL grant, the temporary cell identifier and TAC by selecting arandom access response having a random access preamble identifieridentical with the random access preamble selected by itself (S1001).

3. Scheduled Transmission

If the user equipment UE receives a random access response effective foritself, it respectively processes various kinds of the informationincluded in the random access preamble. Also, the user equipment UEtransmits data stored in the buffer or newly generated data to the basestation BS based on the UL grant (S1003). At this time, the data basedon the UL grant should include the identifier of the user equipment UE.In case of the content based random access procedure, the base stationBS cannot determine which user equipment(s) UE(s) performs the randomaccess procedure because the base station BS should identify the userequipment UE to solve contention later. There are two methods ofincluding the identifier of the user equipment UE in data transmitted tothe base station BS in response to the UL grant. The first method isthat the user equipment UE having a valid cell identifier allocated froma corresponding cell before the random access procedure transmits itscell identifier through an uplink transmission signal corresponding tothe UL grant. On the other hand, the user equipment UE which is notallocated with a valid cell identifier before the random accessprocedure transmits its unique identifier (for example, S-TMSI or randomID). Generally, the unique identifier is longer than the cellidentifier. The user equipment UE which has transmitted the datacorresponding to the UL grant initiates a contention resolution timer(hereinafter, referred to as “CR timer”).

4. Contention Resolution

The user equipment which has transmitted the data including itsidentifier to the base station BS in response to the UL grant includedin the random access response waits for a command of the base station BSto resolve contention. In other words, the user equipment UE tries toreceive the PDCCH to receive a specific message from the base station BS(S1004). Two methods of receiving the PDCCH exist. As described above,if the identifier of the user equipment UE, which is transmitted inresponse to the UL grant, is the cell identifier, the user equipment UEtries to receive the PDCCH by using its cell identifier. If theidentifier of the user equipment UE, which is transmitted in response tothe UL grant, is the unique identifier, the user equipment UE may try toreceive the PDCCH by using the temporary cell identifier included in therandom access response. Afterwards, in case of the former case, if thePDCCH is received through the cell identifier of the user equipment UEbefore the CR timer expires, the user equipment UE determines that therandom access procedure has been performed normally, and ends the randomaccess procedure. In case of the latter case, if the PDCCH is receivedthrough the temporary cell identifier before the CR timer expires, theuser equipment UE identifies the data carried by the PDSCH indicated bythe PDCCH. If the unique identifier of the user equipment UE is includedin the data carried by the PDSCH, the user equipment UE determines thatthe random access procedure has been performed normally, and ends therandom access procedure.

FIG. 11 is a diagram illustrating an operation procedure of UE and BS ina non-contention based random access procedure.

Unlike the contention based random access procedure shown in FIG. 10,the user UE determines that the random access procedure has beenperformed normally by receiving the random access response, and ends therandom access procedure.

1. Random Access Preamble Allocation

As described above, the non-contention based random access procedure maybe performed in case of a handover procedure or a request according tothe command of the base station BS. Of course, the contention basedrandom access procedure may be performed in case of these two cases.

First of all, for the non-contention based random access procedure, theuser equipment UE is allocated with a dedicated random access preamblehaving no possibility of contention from the base station BS (S1101).The user equipment UE may be commanded the random access preamble fromthe base station BS through a handover command or a PDCCH order.

2. Random Access Preamble

The user equipment UE transmits its dedicated random access preambleallocated by the base station BS to the base station BS (S1102).

3. Random Access Response

The user equipment UE receives the random access response from the basestation BS (S1103). The method of receiving the random access responsefrom the base station BS is the same as that in the contention basedrandom access procedure.

Activation/Deactivation of Serving CC

In configuration of carrier aggregation, the base station BS mayconfigure a plurality of serving CCs for the user equipment UE. The basestation BS may identify that some of the plurality of serving CCs maynot be required for communication with the user equipment UE inaccordance with traffic features of services used by the user equipmentUE and radio channel quality of each serving CC. In the meantime,regardless of transmission and reception of the actual data between theuser equipment UE and the base station BS, if the user equipment UEperforms a measurement procedure of a radio channel and monitoring of acontrol signal for data transmission and reception for all the servingCCs included therein, battery consumption of the user equipment UE isincreased. Accordingly, the base station BS may activate the servingCC(s), which is(are) used actually, among the plurality of serving CCsconfigured for the user equipment UE, and may deactivate the servingCC(s) which is (are) not used. The user equipment may reduce its batteryconsumption by not performing measurement of the radio channel andmonitoring of the control signal for the deactivated serving CC(s).

The base station BS may transfer an activation or deactivation commandfor the serving CC to the user equipment UE through the MAC signal. Theuser equipment UE may deactivate the serving CC by using a specifictimer (hereinafter, referred to as deactivation timer). If the userequipment UE receives the activation command for the specific serving CCfrom the base station, BS, it activates the specific serving CC andinitiates the deactivation timer. If the deactivation timer expires, theuser equipment UE deactivates the specific serving CC. If the userequipment receives the PDCCH indicating valid uplink grant or downlinkassignment for the specific serving CC from the base station BS, it mayreset the deactivation timer of the specific serving CC. The basestation may command the user equipment UE to deactivate thecorresponding serving CC through the MAC signal before the deactivationtimer of the activated serving CC expires.

Maximum UE Output (P_(CMAX))

The user equipment UE, which is configured with a plurality of CCsthrough carrier aggregation, may report power headroom (PH) to the basestation BS as follows. In order to report the power headroom, the userequipment UE may perform the following operations.

-   -   The user equipment UE reports the power headroom PH for each        serving CC to the base station BS.    -   In calculating the power headroom PH for each serving CC, the        user equipment UE calculates a maximum output P_(CMAX,c) for the        corresponding CC, and calculates the other output value        excluding the output value currently used in the corresponding        CC from the maximum output P_(CMAX,c) as the power headroom PH.    -   The maximum output P_(CMAX,c) of the user equipment UE for the        serving CC corresponds to the value excluding a power reduction        value applied by the user equipment UE within a maximum power        reduction (MPR) value in accordance with implementation of the        user equipment UE.

In calculating the maximum output P_(CMAX,c), since different values maybe applied to each user equipment UE in accordance with implementationof the user equipment UE within the MPR value, for more exact powerheadroom report (PHR) to the base station BS, the user equipment UEtransmits the PHR, which additionally includes the maximum outputP_(CMAX,c) excluding the power reduction value, to the base station BS.

FIG. 12 is a diagram illustrating an example of a PHR MAC controlelement (CE) format transmitted from a user equipment UE, which includescarrier aggregation, to a base station BS.

In FIG. 12, a “C_(i)” field indicates the presence of a PH filed for theSCC having SCC (that is, SCell) index i. The “C_(i)” field set to 1 mayindicate that the PH for the corresponding SCC is reported, and the“C_(i)” field set to 0 may indicate that the PH for the correspondingSCC is not reported. “R” is a reserved bit and is set to 0. Also, a “V”field indicates whether the PH value is based on a real transmission ora reference format. If V=0, it indicates a real transmission on thePUSCH/PUCCH. If V=1, it indicates that a PUSCH or PUCCH reference formatis used. Moreover, V=0 indicates the presence of an associatedP_(CMAX,c) field. If V=1, it indicates that the associated P_(CMAX,c)field is omitted. A “PH” field indicates a power headroom level, and a“P” field indicates whether the user equipment UE applies power backoffdue to power management. If the P_(CMAX,c) field exists, this fieldindicates a maximum output used to calculate the preceding PH field.

In performing, by the user equipment UE configured with carrieraggregation, the aforementioned time advance maintenance, the simplestmethod is that the UE manages only one uplink time advance. In orderthat the base station BS and the user equipment UE manage the one uplinktime advance, aggregated uplink CCs should be limited to the frequencieswithin the same frequency band. Also, if the same frequency istransmitted and received through antennas of different locations, sincethe distance between the antenna, which transmits and receives thefrequency, and the user equipment UE is varied depending on theantennas, the same time advance cannot be applied to the uplink CCsoperated at the frequency based on the antennas of different locations.Accordingly, in order to allow one uplink time advance maintenance, itis required that the aggregated uplink CCs should be operated on thefrequency (or frequencies) based on the antennas of the same location aswell as the frequencies within the same frequency band. If the uplinkCCs, which belong to the same frequency band and are operated on thefrequencies based on the antennas of the same location, are aggregated,the uplink CCs have the same or like frequency features or uplink timingfeatures as one another, one uplink time advance maintenance may beperformed.

If the user equipment UE manages one uplink time advance, it only has tomanage one time alignment timer, and may determine that the aggregateduplink CCs are synchronized with one another in time advance while thetime alignment timer is being driven. If the user equipment UE managesone uplink time advance, since the user equipment UE only has to acquireone TAC during the random access procedure, it performs the randomaccess procedure through the PCC only. Namely, the user equipment UEdoes not perform the random access procedure through the SCC. Also,since all the uplink CCs have one time advance, the PUCCH is transmittedand received on the PCC only. Namely, the PUCCH is not transmittedand/received on the SCC. Also, the user equipment UE performs radio linkmonitoring for the PCC only, and determines radio link failure for thePCC only. If radio link failure for the PCC is determined, the userequipment UE releases configuration of all the serving CC(s) configuredfor the user equipment UE and enters the RRC idle state RRC_IDLE.Accordingly, the user equipment UE, which manages time advance, does notenter the RRC idle state even though a problem occurs in a radio link ofthe SCC.

However, restrictions that the aggregated uplink CCs use the frequenciesbelonging to the same frequency band and the frequencies based on theantennas of the same location act as frequency management restrictionsof operators. Accordingly, the technology of aggregating the uplink CCsoperated on the frequencies within different frequency bands and/or theuplink CCs operated on the frequencies based on the antennas ofdifferent locations has been requested. In order that the uplink CCsoperated on the frequencies within different frequency bands and/or theuplink CCs operated on the frequencies based on the antennas ofdifferent locations are aggregated, the user equipment UE should managea plurality of time advances for the aggregated uplink CCs. In otherwords, the user equipment UE should manage a plurality of time alignmenttimers.

If the uplink CCs operated on the frequencies within different frequencybands and/or the uplink CCs operated on the frequencies based on theantennas of different locations are aggregated, the uplink CCs havedifferent time advances in accordance with frequency features or uplinktiming features. In order to support a plurality of uplink advances,according to the present invention, the uplink CCs are grouped(hereinafter, time advance group) in accordance with frequency featuresor uplink timing features, and the time alignment timer is managed pertime advance group. In order that the user equipment UE manages the timealignment timer per time advance group, the user equipment UE shouldreceive at least one TAC per time advance from the base station BS.Hereinafter, the time advance group, which includes the PCC, will bereferred to as a PCC group, and the time advance group, which includesonly the SCC(s) without PCC, will be referred to as an SCC group. Oneuser equipment, which is configured with carrier aggregation, may haveat least one PCC group. If SCC(s) having time advance different fromthat of the PCC exists, the user equipment UE may have one or more SCCtime advance groups together with the PCC group. The PCC group mayinclude at least PCC, and may include SCC or not. Each of the SCC timeadvance groups may include one or more SCCs.

In order that the user equipment UE manages the time alignment timer pertime advance group, according to the present invention, the userequipment UE should perform the random access procedure in each timeadvance group. Accordingly, the user equipment UE of the presentinvention performs the random access procedure even on the SCC as wellas the PCC. The present invention suggests that the base station BSconfigures a specific SCC (hereinafter, referred to as specific SCC) forwhich the user equipment UE performs the random access procedure, amongthe SCC(s) included in the SCC time advance group. Hereinafter, the SCCfor which the user equipment UE performs the random access procedurewill be referred to as a special SCC, and a method for managing thespecial SCC in the user equipment UE and the base station BS will besuggested. The SCC(s) having the same time advance as that of thespecial SCC may configure one SCC group together with the special SCC.According to the existing carrier aggregation system, although the stepsS1001 to S1003 of the contention based random access procedure in FIG.10 occur on the PCC only, while according to the present invention,steps S1001 to S1003 of the contention based random access procedure ofFIG. 10 may occur on the special SCC as well as the PCC. Also, accordingto the existing carrier aggregation system, although the steps S1101 toS1103 of the non-contention based random access procedure in FIG. 11occur on the PCC only, whereas according to the present invention, stepsS1101 to S1103 of the non-contention based random access procedure ofFIG. 11 may occur on the special SCC as well as the PCC.

The SCC(s) that uses the same time advance as that of the PCC may beincluded in the PCC group. The SCC(s) that uses the same time advance asthat of the special SCC may be included in the SCC group to which thespecial SCC belongs. Preferably, one SCC group includes only one specialSCC. The user equipment UE of the present invention may perform therandom access procedure through the PCC and the special SCC(s) only. Tothis end, the base station BS of the present invention configuresrelated parameter(s) to allow the user equipment UE to perform therandom access procedure on the special SCC.

The present invention suggests an embodiment that the base station BSindicates to the user equipment UE through the RRC signal whether thecorresponding SCC is the special SCC or a normal SCC, when adding theSCC as the serving CC for the user equipment UE. Alternatively, the basestation BS may transmit information indicating the special SCC among theSCCs configured in the user equipment UE, to the user equipment UE. Thebase station BS may indicate to the user equipment UE whether normalSCC(s), not the special SCC(s), belong(s) to the PCC group or the SCCgroup. If the normal SCC belongs to the SCC group, the base station BSmay indicate, to the user equipment UE, an SCC group to which the normalSCC belongs.

Unlike the existing wireless system where the same time advance isapplied to all the uplink CCs, according to the present invention,different time advances are applied to different time advance groups.Accordingly, if the PUCCH for all the serving CCs is transmitted on thePCC only, the base station BS may not acquire channel state information(CSI), HARQ feedback and scheduling request information, which arerelated to the serving CC(s) which does(do) not belong to the PCC group.Accordingly, the present invention suggests an embodiment that the PUCCHfor the SCC(s) belonging to the SCC group is transmitted and received onthe special SCC of the SCC group. In other words, according to thepresent invention, the PCC is used for transmission(s) of PUCCH for thePCC group only, whereas the SCC set as the special SCC is used for PUCCHtransmission for the SCC group to which the special SCC belongs. Inorder that the user equipment UE may perform PUCCH transmission on thespecial SCC, the base station BS may set the PUCCH resource to the userequipment UE by using the RRC signal. Accordingly, the user equipment UEtransmits the uplink control information associated with the servingCC(s), which belongs (or belong) to the PCC group, to the base stationBS through the PUCCH of the PCC, and transmits the uplink controlinformation associated with the serving CC(s), which belongs (or belong)to the SCC group of the special SCC, to the base station BS through thePUCCH of the special SCC. In other words, if the plurality of timeadvance groups are configured, according to the present invention, theuser equipment UE may transmit the PUCCH even on the special SCC as wellas the PCC, and the base station BS may receive the PUCCH even on thespecial SCC as well as the PCC from the user equipment UE.

In the meantime, the present invention suggests an embodiment that thebase station may configure the user equipment UE to selectively performradio link monitoring for the special SCC, or suggests an embodimentthat the user equipment UE performs radio link monitoring for thespecial SCC. In other words, although the user equipment UE performsradio link monitoring for the PCC only in the existing wireless system,according to this embodiment, the user equipment UE may perform radiolink monitoring for the special SCC (see S1502 of FIG. 15) as well asthe PCC. However, the user equipment UE according to this embodimentdoes not perform radio link monitoring for the normal SCC in the samemanner as the user equipment UE according to the existing wirelesssystem.

Also, the present invention suggests an embodiment that the base stationBS sets the user equipment UE to selectively determine radio linkfailure for the special SCC, or suggests an embodiment that the userequipment UE selectively determines radio link failure for the specialSCC. Although the user equipment UE determines radio link failure forthe PCC only in the existing wireless system, the user equipment UEaccording to this embodiment may selectively determine radio linkfailure for the special SCC as well as the PCC. The user equipment UE,which has determined radio link failure for the special SCC, may releaseconfiguration of all the serving CC(s) within the SCC group to which thespecial SCC belongs. The released configuration may include PUCCHconfiguration of the special SCC. And when the user equipment UEexperiences a radio link failure from the special SCC or serving CC(s)within the SCC group, it shall stop any transmissions and receptionson/from the special SCC and serving CC(s) within the SCC group. Also,when the user equipment UE experiences a radio link failure of thespecial SCC, the user equipment UE reports a radio link failure of theSCC group to which the special SCC belongs (see S1503 of FIG. 15).However, although radio link failure for the special SCC is determined,the configuration of the serving CC(s) of the other time advance groupnot the time advance group to which the special SCC belongs ismaintained as far as radio link failure for the PCC is not determined,and the user equipment UE does not enter the RRC idle state (RRC_IDLE).If the radio link failure for the PCC is determined, the base station BSand the user equipment UE release connection of all the serving CC(s)configured in the user equipment UE, and the user equipment UE entersthe RRC idle state.

Also, the present invention suggests an embodiment that the special SCCis designated as a reference serving CC of path loss for the SCC groupto which the special SCC belongs. The user equipment UE calculatesdownlink path loss for each serving CC configured in the user equipmentUE, and reflects the downlink path loss in determination of the uplinktransmission power. The base station BS selects the special SCC as areference serving SCC used to determine a reference signal power for theSCC group to which the special SCC belongs, and transmits the selectedone to the user equipment UE. The user equipment UE may calculate pathloss of the SCC(s) within the SCC group with reference to the path lossof the special SCC of the SCC group.

Also, the present invention suggests an embodiment that the userequipment UE and the base station BS release or deactivate theconfiguration of all the serving CC(s) including the special SCC of thecorresponding time advance group if the user equipment UE determinesthat the random access procedure to the special SCC has been failed. Theuser equipment UE according to this embodiment may report the fact thatthe random access procedure to the special SCC has been failed, to thebase station BS. If the random access procedure to the special SCC isfailed, the user equipment triggers or starts the random accessprocedure to the PCC to continue to perform the random access procedure.The user equipment UE may determine that the random access procedure isfailed if retransmission of the random access preamble by means of theuser equipment reaches the maximum value set by the base station BS.

Also, the present invention suggests an embodiment that release for thespecial SCC is interpreted as release of all the serving CCs within theSCC group to which the special SCC belongs. If the user equipment UEreceives a command to release the special SCC from the base station BS,it releases all the serving CC(s) within the SCC group to which thespecial SCC belongs, as well as the special SCC.

Also, the present invention suggests an embodiment that the userequipment UE reports transmission power information related to the timeadvance group to the base station BS in reporting the power headroom ofthe user equipment UE to the base station BS. For example, thetransmission power information per time advance group may be a sum oftransmission powers that may be used in the corresponding time advancegroup. In other words, the transmission power information may bereported from the user equipment UE to the base station BS in the formof P_(CMAX,c) per group (hereinafter, referred to as P_(CMAX,g)). Theuser equipment UE may report the P_(CMAX,g) to the base station BSthrough MAC CE for the power headroom report (PHR) described withreference to FIG. 12.

Also, the present invention suggests an embodiment that one deactivationtimer is set per time advance group. In the existing system, thedeactivation timer is set per SCC, whereas the deactivation timer is setper time advance group in the present invention. Also, the same value isapplied to each SCC in the existing system even though the deactivationtimer is set per SCC, a respective value may be applied to each group inthe present invention. Accordingly, UE complexity may be reduced. Thebase station BS may set and transmit one deactivation timer per SCCgroup of the user equipment UE. The base station BS may set thedeactivation timer for the special SCC only in the SCC group andtransmit the set timer to the user equipment UE, and may not set thedeactivation timer for the other SCC(s) within the SCC group. If thespecial SCC is activated, the user equipment UE initiates thedeactivation timer for the special SCC. The user equipment UE may resumethe deactivation timer of the special SCC only if the PDCCH related tothe special SCC is received. If the deactivation timer of the specialSCC expires, the user equipment UE may deactivate all the serving CC(s)within the SCC group to which the special SCC belongs, as well as thespecial SCC. The base station BS may set the deactivation timer per SCCfor the SCC(s) to which the special SCC belongs and transmit the setdeactivation timer to the user equipment UE, or may set one deactivationtimer for the PCC group and transmit the set deactivation timer to theuser equipment UE. If the deactivation timer of the SCC which belongs tothe PCC group expires, the user equipment UE may deactivate the SCCwhich belongs to the PCC group.

FIG. 13 is a diagram illustrating a random access procedure according tothe embodiments of the present invention.

Referring to FIG. 13, the base station BS adds the special SCC (that is,special SCell) through the RRC signal (S1301, S1501). The base stationBS may designate the SCC as the special SCC while adding the SCC, or mayset the special one of the SCCs configured as the serving CCs andindicate the special SCC to the user equipment UE. The RRC signalrelated to addition or setting of the special SCC may includeinformation related to the deactivation timer, which will be used in theSCC group configured by the special SCC. Also, the RRC signal mayinclude a related parameter that allows the user equipment UE to performthe random access procedure on the special SCC.

The user equipment UE performs the random access procedure by using theSCC only indicated as the special SCC of the SCCs within the SCC groupto acquire the TAC for the SCC group (S1302, S1504). In more detail, theuser equipment UE may transmit the random access preamble to the basestation BS on the special SCC, and may receive the random accessresponse, which includes the random access preamble identifiercorresponding to the random access preamble, from the base station BS.The random access response may be received on the special SCC. The userequipment UE may apply the TAC within the random access response to theSCC(s) within the SCC group. If the user equipment has a plurality ofSCC groups, it performs the random access procedure to the special SCCof the corresponding SCC group and acquires the TAC for each SCC group.The user equipment UE may acquire the TAC for the PCC group byperforming the random access procedure to the PCC. In more detail, theuser equipment may transmit the random access preamble to the basestation BS on the PCC, and may receive the random access response, whichincludes the random access preamble identifier corresponding to therandom access preamble, from the base station BS. The random accessresponse may be received on the PCC. The user equipment UE may apply theTAC within the random access response to the PCC within the PCC group,and the SCC(s) if any.

The user equipment UE transmits the PUCCH(s) carrying the uplink controlinformation associated with the SCC(s) belonging to the SCC group, tothe base station BS on the special SCC (S1303, S1505). The userequipment UE may transmit the uplink control information associated withthe serving CC(s) belonging to the PCC group on the PUCCH(s) through thePCC. PUCCH transmission on the special SCC may include CSI, HARQfeedback information, etc., which are associated with all the SCCswithin the SCC group configured as the SCCs based on the same timeadvance as that of the special SCC. The PUCCH transmission on the PCCmay include CSI, HARQ feedback information, etc., which are associatedwith all the serving CCs within the PCC group configured as the servingCCs based on the same time advance as that of the PCC. The uplinkcontrol information of the serving CCs within one time advance group maybe transmitted or received on one PUCCH, or may be transmitted orreceived to or from the base station BS on the respective PUCCH perserving CC.

If there is a problem in the random access procedure to the special SCC,the user equipment UE may report the problem to the base station throughthe RRC signal (S1304).

FIG. 14 is a block diagram illustrating a transmission apparatus 10 anda reception apparatus 20, which perform the present invention.

The transmission apparatus 10 and the reception apparatus 20respectively include a radio frequency (RF) unit 13, 23 for transmittingor receiving a radio signal carrying information and/or data, signal ormessage, a memory 12, 22 storing various kinds of information related tocommunication within a wireless communication system, and a processor11, 21 connected with the RF unit 13, 23 and the memory 12, 22 andconfigured to control the memory 12, 22 and/or the RF unit 13, 23 toallow the corresponding apparatus to perform at least one of theaforementioned embodiments of the present invention.

The memory 12, 22 may store a program for processing and control of theprocessor 11, 21 and temporarily store input/output information. Thememory 12, 22 may be used as a buffer.

The processor 11, 21 generally controls the overall operation of variousmodules of the transmission apparatus or the reception apparatus. Inparticular, the processor 11, 21 may perform a controller function forimplementing the aforementioned embodiments of the present invention.The processor 11, 21 may be referred to as a controller, amicrocontroller, a microprocessor, and a microcomputer. The processor11, 21 may be implemented by hardware, firmware, software, or theircombination. If the present invention is implemented by hardware,application specific integrated circuits (ASICs), digital signalprocessors (DSPs), digital signal processing devices (DSPDs),programmable logic devices (PLDs), and field programmable gate arrays(FPGAs), which are configured to perform the present invention, may beprovided in the processor 11, 21. Meanwhile, if the present invention isimplemented by firmware or software, the firmware or software may beconfigured to include a module, a procedure, or a function, whichperforms functions or operations of the present invention. The firmwareor software configured to perform the present invention may be providedin the processor 11, 21 or may be stored in the memory 12, 22 and thenmay be driven by the processor 11, 21.

The processor 11 of the transmission apparatus 10 performs predeterminedcoding and modulation for a signal and/or data scheduled from theprocessor 11 or a scheduler connected with the processor 11 andtransmitted to the outside, and then the coded and modulated data to theRF unit 13. For example, the processor 11 converts desired data streamsinto K number of layers through demultiplexing, channel coding,scrambling, modulation, etc. The coded data streams may be referred toas codewords, and are equivalent to transport blocks which are datablocks provided by a medium access control (MAC) layer. One transportblock (TB) is coded into one codeword, wherein each codeword istransmitted to the reception apparatus in a type of one or more layers.For frequency uplink conversion, the RF unit 13 may include anoscillator. The RF unit 13 may include N_(t) number (N_(t) is a positiveinteger greater than 1) of transmitting antennas.

A signal processing procedure of the reception apparatus 20 isconfigured by an inverse procedure of the signal processing procedure ofthe transmission apparatus 10. Under the control of the processor 21,the RF unit 23 of the reception apparatus 20 receives a radio signaltransmitted by the transmission apparatus 10. The RF unit 23 may includeN_(r) number of receiving antennas. The RF unit 23 frequencydown-coverts each of the signals received through the receiving antennasto recover baseband signals. The RF unit 23 may include an oscillatorfor frequency down-conversion. The processor 21 may perform decoding anddemodulation for the radio signals received through the receivingantennas to recover data originally intended to be transmitted from thetransmission apparatus 10.

The RF unit 13, 23 includes one or more antennas. The antennas maytransmit the signals processed by the RF unit 13, 23 to the outside orreceive the radio signals from the outside and transfer the radiosignals to the RF unit 13, 23 under the control of the processor 11, 21in accordance with one embodiment of the present invention. The antennasmay be referred to as antenna ports. Each antenna may correspond to onephysical antenna or may be configured by combination of physical antennaelements more than one. The signal transmitted from each antenna cannotbe decomposed any more by the reception apparatus 20. The referencesignal (RS) transmitted to correspond to the corresponding antennadefines the corresponding antenna in view of the reception apparatus 20,and allows the reception apparatus 20 to perform channel estimation forthe antenna regardless of the fact that the channel is a single radiochannel from one physical antenna or a composite channel from aplurality of physical antenna elements including the above antenna. Inother words, the antenna is defined such that a channel transferringsymbols on the antenna may be obtained from the channel to which othersymbols on the same antenna are transferred. The RF unit that supports amulti-input multi-output (MIMO) function for transmitting and receivingdata using a plurality of antennas may be connected with two or moreantennas.

In the embodiments of the present invention, the user equipment UE isoperated as the transmission apparatus 10 on the uplink and as thereception apparatus 20 on the downlink. In the embodiments of thepresent invention, the base station BS is operated as the receptionapparatus 20 on the uplink and as the transmission apparatus 10 on thedownlink.

The processor (hereinafter, referred to as BS processor) of the basestation BS according to the present invention may group the uplink CCsconfigured in the user equipment, which is configured with carrieraggregation, as one or more time advance groups in accordance withfrequency features. The BS processor may configure the PCC group byusing the PCC and the SCC(s) having the same frequency features as thoseof the PCC, and if the SCC(s) having the frequency features differentfrom those of the PCC, that is, the SCC(s), which cannot use the sametime advance as that of the PCC, exist, the BS processor may configureone or more SCC groups by using the SCC(s). If the SCCs, which cannotuse the same time advance as that of the PCC, have different frequencyfeatures, these SCCs may be configured different SCC groups. The BSprocessor may configure one special SCC per SCC group, and may indicatethe special SCC for each SCC group to the user equipment UE bycontrolling the RF unit (hereinafter, referred to as BS RF unit) of thebase station BS. The BS processor according to one embodiment of thepresent invention may control the BS RF unit to transmit RRC signalindicating whether the corresponding SCC is the special SCC or normalSCC, when adding the SCC as the serving CC for the user equipment UE. Ifthe SCC is used as the normal SCC and is not included in the PCC group,the BS processor may control the BS RF unit to transmit RRC signalindicating which group includes the SCC, to the user equipment UE. TheRF unit (hereinafter, referred to as UE RF unit) of the user equipmentUE may receive RRC signal(s) from the base station BS, and may identifythe time advance group(s) and the serving CC which will be a referenceof the time advance in each time advance group. The UE processor maycontrol the user equipment UE RF unit to perform the random accessprocedure by using the PCC for the serving CC(s) belonging to the PCCgroup, and may acquire the TAC for the PCC group on the PCC. For theserving CC(s) belonging to the SCC group, the UE processor may controlthe user equipment UE RF unit to perform the random access procedure byusing the serving CC set as the special SCC within the corresponding SCCgroup, and may acquire the TAC for the corresponding SCC group on thespecial SCC of the corresponding SCC group. The UE processor applies theTAC received on the PCC to the serving CC(s) belonging to the PCC groupand applies the same time alignment timer to all the serving CCsbelonging to the PCC group, so as to manage the uplink time advance.Also, the UE processor applies the TAC received on the special SCC ofthe SCC group to the serving CC(s) belonging to one SCC group andapplies the same time alignment timer to all the serving CCs belongingto the SCC group, so as to manage the uplink time advance. The UEprocessor may apply different TACs and/or different time alignmenttimers to the serving CCs belonging to different time advance groups.

Also, the BS processor according to one embodiment of the presentinvention may control the BS RF unit to transmit RRC signal indicatingPUCCH resource, which will be used on the special SCC, to the userequipment UE. The processor of the user equipment, which includes aplurality of time advance groups, controls the user equipment UE RF unitto transmit uplink control information associated with the serving CC(s)belonging to the PCC group to the base station through the PUCCH(s) ofthe PCC, and transmits uplink control information associated with theserving CC(s) belonging to the SCC group to the base station BS throughthe PUCCH(s) of the special SCC.

Also, the BS processor according to one embodiment of the presentinvention may configure the user equipment UE to selectively performradio link monitoring for the special SCC. Alternatively, the userequipment UE may selectively perform radio link monitoring for thespecial SCC. The UE processor according to one embodiment of the presentinvention may perform radio link monitoring for the special SCC as wellas the PCC.

Also, the BS processor according to one embodiment of the presentinvention may configure the user equipment UE to selectively determineradio link failure for the special SCC. Alternatively, the userequipment UE may selectively determine radio link failure for thespecial SCC. In other words, the UE processor according to oneembodiment of the present invention may selectively determine radio linkfailure for the special SCC as well as the PCC. If the UE processordetermines radio link failure for the special SCC, it may releaseconfiguration of all the serving CC(s) within the SCC group to which thespecial SCC belongs.

Also, if the random access procedure to the special SCC is failed, theUE processor and the BS processor according to one embodiment of thepresent invention may release or deactivate the configuration of all theserving CC(s) including the special SCC of the corresponding SCC group.If the random access procedure to the special SCC is failed, the UEprocessor according to one embodiment of the present invention mayreport the fact that the random access procedure to the special SCC hasbeen failed, to the base station BS. If the BS RF unit receives thereport that the random access procedure to the special SCC has beenfailed, from the user equipment UE, the BS processor may control the BSRF unit to transmit RRC signal releasing the configuration of all theserving CC(s) of the SCC group to which the special SCC belongs or MACsignal deactivating the configuration to the user equipment UE. If therandom access procedure to the special SCC is failed, the UE processormay trigger or start the random access procedure to the PCC. The UEprocessor may determine that the random access procedure is failed ifretransmission of the random access preamble by means of the userequipment UE reaches the maximum value set by the base station BS.

Also, the BS processor according to one embodiment of the presentinvention may command the user equipment UE to release or deactivate allthe serving CC(s) within the SCC group to which the special SCC belongs,by commanding the user equipment UE to release or deactivate the specialSCC. The BS processor may command the user equipment UE to release theconfiguration of all the serving CC(s) within the SCC group bycontrolling the BS RF unit to transmit RRC signal, which releases theconfiguration of the serving CC configured as the special SCC in the SCCgroup, to the user equipment UE. The BS processor may deactivate all theserving CC(s) within the SCC group by controlling the BS RF unit totransmit MAC signal, which indicates deactivation of the serving CCconfigured as the special SCC in the SCC group, to the user equipmentUE. If the UE RF unit receives the signal indicating release (ordeactivation) for the special SCC from the base station BS, the UEprocessor may release (or deactivate) all the serving CC(s) within theSCC group to which the special SCC belongs.

Also, the BS processor according to one embodiment of the presentinvention may configure one deactivation timer per time advance groupand transmit the deactivation timer per time advance group to the userequipment UE by controlling the BS RF unit. UE RF unit may receive thedeactivation timer per time advance group from the base station BS. Ifthe special SCC is activated, the UE processor initiates thedeactivation timer for the special SCC. Also, the UE processor mayresume the deactivation timer of the special SCC only if the PDCCHsignal related to the special SCC is received. If the deactivation timerof the special SCC expires, the UE processor may deactivate all theserving CC(s) within the SCC group to which the special SCC belongs. TheBS processor may set the deactivation timer per SCC belonging to the PCCgroup and control the BS RF unit to transmit the deactivation timer perSCC within the PCC group, or may set one deactivation timer for the PCCgroup and control the BS RF unit to transmit one deactivation timer forthe PCC group to the user equipment UE. If the deactivation timer of theSCC belonging to the PCC group expires, the UE processor may deactivatethe SCC belonging to the PCC group.

In the embodiments of the present invention, although the PCC (that is,PCell) and the special SCC (that is, special SCell) may be used for therandom access procedure, they are identified from each other in view ofthe following aspects. Since the SCC is configured after RRC connectionis established, the special SCC may be configured only if the userequipment UE is in the RRC connection state. Accordingly, the PCC may beused when the user equipment UE of the RRC idle state enters the RRCconnection state, whereas the special SCC cannot be used when the userequipment of the RRC idle state enters the RRC connection state. Also,although the user equipment UE which is in the RRC connection state hasone PCC, the special SCC may exist as much as the number of SCC groupsconfigured in the user equipment UE. Also, special downlink controlinformation is transmitted or received through the PCC only. Forexample, the user equipment UE applies system information acquisitionprocedure to the PCC only. For another example, non access stratum (NAS)mobility information and security input are transmitted or receivedthrough the PCC only. Also, in order to generate a security parameterfor ciphering, the PDCP layer uses a physical cell identifier (PCI) ofthe PCC, and does not use the PCI of the SCC including the special SCC.Also, if the user equipment UE includes a plurality of serving CCs, thebase station may activate or deactivate the special SCC but cannotdeactivate the PCC. The special SCC is deactivated at the time when itis added as the serving CC and immediately after handover is performed,the serving CC which is the PCC is activated and is not deactivated asfar as the PCC is not changed to another serving CC.

According to the present invention, the uplink CCs operated on thefrequencies within different frequency bands and/or the uplink CCsoperated on the frequencies based on the antennas of different locationsmay be aggregated. Also, different time advances may be applied to theuplink CCs having different frequency features.

Those skilled in the art will appreciate that the present invention maybe carried out in other special ways than those set forth herein withoutdeparting from the spirit and essential characteristics of the presentinvention. The above embodiments are therefore to be construed in allaspects as illustrative and not restrictive. The scope of the inventionshould be determined by the appended claims and their legal equivalents,not by the above description, and all changes coming within the meaningand equivalency range of the appended claims are intended to be embracedtherein. It is also obvious to those skilled in the art that claims thatare not explicitly cited in each other in the appended claims may bepresented in combination as an embodiment of the present invention orincluded as a new claim by a subsequent amendment after the applicationis filed.

INDUSTRIAL APPLICABILITY

The aforementioned embodiments of the present invention may be appliedto the base station, the user equipment, other equipment in the wirelesscommunication systems.

1-13. (canceled)
 14. A method for transmitting, by a user equipmentconfigured with a secondary cell (SCell) group comprising a plurality ofSCells, an uplink signal to a base station, the method comprising:receiving information indicating a special SCell for addition of thespecial SCell into the SCell group or designation of the special SCellamong the plurality of SCells within the SCell group; and performing arandom access procedure on the special SCell, wherein the SCell groupdoes not include a Primary Cell (PCell).
 15. The method of claim 14,further comprising transmitting an uplink signal for the plurality ofSCells within the SCell group to the base station on the special SCellthrough a physical uplink control channel (PUCCH).
 16. The method ofclaim 14, further comprising: receiving a timing advance command (TAC)for the special SCell from the base station in response to the randomaccess procedure performed on the special SCell; and applying the TAC toevery cell within the SCell group.
 17. The method of claim 16, furthercomprising: receiving information indicating release of the specialSCell from the base station; and releasing every cell within the SCellgroup.
 18. The method of claim 16, further comprising: receivinginformation indicating deactivation of the special SCell from the basestation; and deactivating every cell within the SCell group.
 19. Themethod of claim 18, further comprising: receiving a deactivation timerfor the special SCell from the base station; and applying thedeactivation timer to every cell within the SCell group.
 20. The methodof claim 14, further comprising releasing or deactivating every cellwithin the SCell group in case of radio link failure for the specialSCell.
 21. The method of claim 14, wherein, among the plurality ofSCells within the SCell group, only the special SCell is allowed toperform random access.
 22. The method of claim 14, wherein: the userequipment is capable of performing radio link monitoring for the spciallSCell; and the user equipment is capable of reporting a radio linkfailure (RLF) of the SCell group when a RLF of the special SCell isdetected.
 23. A method for receiving, by a base station, an uplinksignal from a user equipment configured with a secondary cell (SCell)group comprising a plurality of SCells, the method comprising:transmitting information to the user equipment, the informationindicating a special SCell for addition of the special SCell into theSCell group or designation of the special SCell among the plurality ofSCells within the SCell group; and performing the random accessprocedure with the user equipment on the special SCell, wherein theSCell group does not include a Primary Cell (PCell).
 24. The method ofclaim 23, further comprising receiving an uplink signal for the one ormore SCells within the SCell group from the user equipment on thespecial SCell through a physical uplink control channel (PUCCH).
 25. Themethod of claim 23, further comprising transmitting a timing advancecommand (TAC) for the special SCell to the user equipment in response tothe random access procedure performed on the special SCell.
 26. Themethod of claim 25, further comprising: transmitting informationindicating release of the special SCell to the user equipment; andreleasing every cell within the SCell group.
 27. The method of claim 25,further comprising: transmitting information indicating deactivation ofthe special SCell to the user equipment; and deactivating every cellwithin the SCell group.
 28. The method of claim 27, further comprisingtransmitting a deactivation timer for the special SCell to the userequipment for every cell within the SCell group.
 29. The method of claim23, wherein, among the plurality of SCells within the SCell group, onlythe special SCell is allowed to perform random access.
 30. The method ofclaim 23, wherein: the base station is capable of receiving a report ona radio link failure (RLF) of the SCell group from the user equipment;and the RLF is detected based on radio link monitoring only for thespecial SCell among the plurality of SCells.
 31. A user equipment, whichis configured with a plurality of a secondary scell (SCell) groupcomprising a plurality of SCells, for transmitting an uplink signal to abase station, the user equipment comprising: a radio frequency (RF) unitconfigured to transmit or receive a radio signal; and a processorconfigured to control the RF unit to: receive information indicating aspecial SCell for addition of the special SCell into the SCell group ordesignation of the special SCell among the plurality of SCells withinthe SCell group; and perform the random access procedure on the specialSCell, wherein the SCell group does not include a Primary Cell (PCell).32. A base station for receiving an uplink signal from a user equipment,which is configured with a plurality of a secondary scell (SCell) groupcomprising a plurality of SCells, the base station comprising: a radiofrequency (RF) unit configured to transmit or receive a radio signal;and a processor configured to control the RF unit to: transmitinformation indicating a special SCell for addition of the special SCellinto the SCell group or designation of the special SCell among theplurality of SCells within the SCell group, to the user equipment; andperform the random access procedure with the user equipment on thespecial SCell, wherein the SCell group does not include a Primary Cell(PCell).